Large Mileage Loss

[86 720]

Went from 28 MPG to just over 18MPG. Truck isn't running bad, idles fine, and there isn't a fuel leak that I can smell.

Thinking it may be vacuum. Any ideas of what it might be or which vacuume hose?

Standard carb, could just need a re-build or new...

[fastboatman29212]

If you were getting 28 mpg, then I need to rebuild my carb, cause I'm only getting 22mpg, and I thought that was about average. I sure would like to drive it more if it got better gas mileage. Great, you just gave me another project to do. Oh well. It should be fun.

[lambohaha]

Mine gets in the neighborhood of about 25ish or so. So yep, you got to get busy and make another one of your fine "How To`s" for us lol.

[PEZi]

Odd.... I never got more than 24 with the stock carb! I suppose that may have something to do with altitude, though.

[drumaniac3000]

I'm seeing high teens with mostly highway driving with my bone stock z24.

[captainzeros]

I had been seeing 25+, but lately I've dropped to around 22.5 consistently regardless of how aggressively I drive. Then again, my secondary is all screwed up right now.

Z22 2wd truck.

[synack7350]

sounds like you're dumping gas. Are your plugs fouled?

[woodbutcher5691]

Could be the summer blend gas is not as good as winter blend affecting your M.P.G.s. This subject has popped up before on other forums around this time of year. I don't know if there is any truth to it though. I'm seeing +/- 20 M.P.G.s, seems like mine have dropped a little too.

[fastboatman29212]

We should all be aware that factory mpg ratings for these trucks were calculated before ethanol enriched (diluted??? ) fuel existed. All vehicles get better mpg with no ethanol. Anyone have the 2WD and 4WD mpg factory ratings for these trucks? (They were always predicted and never actually got what the rating said anyway, but it would be interesting to know.)

[Rev_D21]

Have you hooked up a vac gauge to it yet? What's it reading and what's the needle doing?

[86 720]

Guess I should quit bitchin with my mileage huh?

I did notice it happened after I changed the vac lines, but it's been well over a month now since I did that. I went back over all the lines, and they are all ok.

Haven't done the vac gauge. I'll need to go buy one, where do I hook it to?

[synack7350]

i'm avg'ing 25mpg with the 32/36. less for highway but I'm running the 4speed AT.

[flinterman2000]

Do a general tune up and see what happens. Your milage should improve regardless of the blend of fuel.